Radio receiving apparatus



March 25, 1930. a. MINNIUM 1,751,706

RADIO RECEIVING AREARATUS Filed May 6, 1926 RADlo FREQUENCY CHOKE.

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BYRON B. MINNIUM, OF CHICAGO, ELLENOIS, ASSIGNOR, BYMESNE ASSIGNMENTS,

TO STORY 85 CLARK RADIO CORP, OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE RADIO RECEIVING APPARATUS Application filed May a, 1926/ Serial No. 10?,015.

This invention relates to radio receiving apparatus, andmore particularly to apparatus of this kind having vacuum tube amplification.

Generally stated, the object of the invention is to improve the receiving efiiciency of a radio receiving set of the kind shown and described and covered broadly in prior application No. 754,501, filed December 8,1924, in which a VVheatstone bridge arrangement is involved for preventing so-called oscillation in radio frequency amplifier circuits of this general type, and to thereby insure against any interference of this kind with thepr0per reception of the incoming signal.

A special object, with a view to improving the receiving qualities of the receiving set, andthe amplification and otherldesired re sults, is to providea novel andimproved circuit arrangement whereby a continuous vi-ded from the filament of the vacuum tube through the secondary of the transformer or repeating coil, and then through 1DCLUCtitDCQ to the filament of the lamp or vacuum tube, to

insure the desired improvement in the Operation of the receiving set, as willhereinafter more fully appear. I

Tothe foregoing and other useful ends,- the invention consists 1n the matters hereinafter set forth and claimed, and shown in the .accompanylng drawings, in Wl'llCll,

Fig. 1 1s a diagram of aracho receiving apparatus involving the principles of the invencoil 4: of said transformer has one terminal connected to the grid 5 of the first vacuum tube, and the filament 6 of said tube is connected through the variable condenser 7 with the other terminal of said secondary coil. The condenser 7 is connected in series with a similar condenser 8, which latter is connected at one side to the upper terminal of the coil 4; and, therefore, tothe filament of the tube. The middle point of the connection between the two condensers is connected to the filament as shown. The condenser 7' and thevlower terminal of the coil 4 are connect'edthrough the stoppingicondenser 9 to one terminal of the primary 10 of v the next repeating coil or transformer, and this same terminal of this.

primary coil 10 is connectedto the plate 11 of said vacuum tube, substantially as shown in thediagrams, The upper terminal of the inductance coil ;12 is connected to the connection between the filament and the middle point of'the connection between the two con-e densers 7 and 8, as is also the variable condenser13, whilethe lower terminal of the coil 12 is connected to the connection between the condenser 9 and thelower terminal of the coil 4, as shown, and, again, the condenser 13 is similarly connected, wherebv the coil 12 and the condenser 13 are connected'in multiple and in shunt of the condenser 7 previously mentioned. i

In this way, and looking at Fig. 2, which latter is laid out in the form of a VVheatstone bridge, itwill be seen that this bridge comprises the usual four arms connected between the points 14, 15, 16 and 1.7, these points being the junctions between the arms of the li Vheatstone bridge arrangement thus formed. In this way, the previously mentioned condenser 7 is in the armbetween the points 14 and 17, while thecondenser 8 is in the armbetween'the points 14 and 15, so that each of these two arms has adjustable capacity there- 7 the bridge connected between the'points 15 and 16, as shown. 'Consequently,the condenser 13 and the coil 12, as shown in Fig. 2, are connected in multiple and are in shunt of the condenser7, which latter forms one of the capacities of the VVheatstone bridge arrangement. The coil or winding 4 previously mentioned is connected between the points 15' and 17, as shown in Fig. 2, whilethe coil or winding 10 previously mentioned is connected through battery and between the points 14 and 16 of the lrVheatstone bridge arrangement.

In this way, therefore, it will be seen that an unbroken metallic path can be traced from the grid 5 around through the coil 4, and then through the inductance 12 to the filament 6, whereby the grid to filament capacity, if any, is in the metallic circuit including the coils 4 and 12' of the circuit arrangement shown and described, this grid to filament capacity being indicated in dotted lines in Fig. 2 of the drawings, and beneficial effects will result from this combination and circuit arrangement, in the operation of the receiv ing set.

The principal advantage to be obtained, in the use of the radio frequency choke coil 12, is to remedy the difficulty which is often encountered when a radio receiving set is employed inclose proximity to, or in the neighborhood of, an electric power plant where the current is frequently turned on and off, as in the operation of elevators. In such case, the receiving set is liable to be affected, as a direct current charge is -liable to be put on the grid of thevacuum tube, and this will momentarily render the vacuum tube inoperative for the reeeiving'of signals. This is liable to happen, with the"VVheatstone bridge arrangement shown and described, and hence the addition of the coil 12, in combination with the W'heatstone bridge ar rangement, isfoundto be desirable andhelpful in situations of the kind described. The coil 12 will permit the passage of direct current charges, so that they can gradually leak oii', but this coil will not permit passage therethrough of the radio signal currents. The same arrangement is shown, it will be seen. for the second stage of amplification, in Fig. 1 of the drawings, and it will be understood that the coil 12 can be used in combination with each and every vacuum tube or step of amplification, in any receiving set where the WVheatstone bridge arrangement shown and described is employed, or in any receiving set circuit in which capacity is interposed in the path between the grid and the filament, so that without the coil no metallic path will exist between the grid and the filament. Also, of course, the coil 12 could be connected directly across from the terminal of the grid to the terminal of the filament and produce good results, but in practice it is found preferable to include the secondary 4 in series with the coil 12, in the metallicpath between the grid and the filament. V

Without disclaiming anything, and .with out prejudice to any novelty disclosed, what I claim as'my invention is: p H 1. Aradio receiving apparatus comprising a vacuum tube having afilamentanda grid and a plate, elements forming in eifect a lVheatstone bridge arrangement with substantially pure capacity only forming each arm of said bridge, the secondary of a re peating coil being connected between opposite junctions of said bridge, one such capacity being formed by the grid to plate capacity of said tube, to thereby suppress oscillation of the tube, and instrumentalities forming an unbroken metallic path through the secondary with inductance therein between the grid and the filament of said vacuum tube, said inductance permitting the passage of direct current charges but preventing the passage of radio signals.

2. Radio receiving apparatus asset forth in claim 1, said instrumentalities comprising said inductance in shunt of one arm of said Wheatstone bridge arrangement.

3. Radio receiving apparatus as set forth in claim 1, said instrumentalities comprising said inductance in shunt of one arm of said Wheatstone bridge arrangement, and variable capacity connected in multiple with said inductance.

4. Radio receiving apparatus asspecified.

in'claim 1, the capacity in two of said arms being adjustable for tuning the bridge t resonance. 7 7 s 5. Radio receiving apparatus as specified in claim 1, comprising means fortuning said bridge to resonance.

6. In radio receiving apparatus, the combination of a vacuum tube having a-grid and a plate and a filament, a repeating coil having a secondary, instrumentalities forming with said secondary an unbroken metallic path having inductance therein between said grid and said filament, and means for tuning the apparatus to resonance, said inductance permittingthe passage of direct current but pre venting the passage of radio signals.

7. Radio receivingv apparatus as specified in claim 6, said instrumentalities comprising inductance connected between one terminal of said filament and one terminal of said secondary.

BYRON B. MINNIUM. 

